Synthesis of TiN and TiNxCy: Optimization of reaction parameters

Titanium nitride and titanium carbide are hard materials with very high melting points, high density and unique physical and electrical properties. Consequently they have special applications as additives for reinforcement of composite materials. Synthesis of titanium nitride, titanium carbide, and the solid solution of the two by carbothermal reduction of titanium dioxide (titania) is economically attractive and is the topic of numerous studies. Here we optimize the reaction parameters leading to an efficient synthesis of titanium nitride powder. A two-level-factorial experimental design is used to investigate the effects of the following five parameters: a, reaction temperature; b, the residence time at that temperature; c, the morphology of the starting materials; d, the level of impurities in the raw materials mix, and e, the methods used to prepare the raw materials mixes. Thus, a five-dimensional ''window of work'' polygon is defined in the five-dimensional parameter space. The reaction parameters are then optimized within the boundaries of that polygon. The results show interactions between the effects of these parameters. We conclude that there are two regions inside the ''window work'' where the desired TIN product was obtained. These two recommended regions of work, for this furnace design, gas flow rate, raw materials etc., are therefore: (1) T = 1350 degrees C; t = 180 min, carbon content = 100% carbonized cotton, chlorides content = 0%, and mixing time = 7 min, and (2) T = 1260 degrees C, t = 180 min, carbon content = 100% graphite powder, chlorides content = 0%, and mixing time = 30 min.